Wednesday December 19 2012
Menus with more information may help you make healthy choices
“Got no willpower? Try a menu that states how many miles you'll need to walk to burn off dinner” the Daily Mail writes, also reporting that menus which say how far you have to walk to burn off your favourite foods really can help in the “battle of the bulge”.
This and related headlines are based on a study of US adults who were split into the following four groups:
- one group given a fast-food menu with no nutritional information
- one group given menus with calorie information only
- one group given menus with calorie information and minutes to walk to burn those calories
- one group given menus with calorie intake and how far you have to walk to burn off the calories
They found that out of the four groups, people given calorie information and information on how far they would have to walk to burn them off ordered fewer calories (826 calories) while those given no nutritional information ordered the most (1,020).
Limitations of the study include:
- preliminary results were obtained in a relatively artificial environment (people were ordering fast food online)
- participants were mainly middle-aged US women seeking to lose weight
Hence, results may not necessarily be applicable to other groups and situations. Still, this interesting study highlights the potentially large psychological influence that different food labelling can have on individual food choices.
This raises the question of whether adding information along these lines to UK food labels would help consumers to make an informed decision about their consumption of calories.
Further research is needed to answer this question and should attempt to replicate a more real-life fast food (or other food) ordering scenario in other more diverse groups.
Where did the story come from?
The study was carried out by researchers from the University of North Carolina and was funded by a grant from the University Research Council at the University of North Carolina.
The study was published in the peer-reviewed science journal Appetite.
The Daily Mail reported the study accurately.
What kind of research was this?
This was a randomised controlled trial (RCT) that aimed to examine the effect of physical activity-based labels on the calorie content of meals selected from a made-up fast food menu.
Most RCTs aim to be double blind, however, this was not practical in this RCT as participants and researchers would obviously know what type of food labels they were reading.
Curbing the rise in obesity levels in developed countries is a public health priority as obesity is a significant risk factor for a range of health problems, including heart disease, stroke, hypertension and type 2 diabetes.
Food labelling is just one avenue that is explored by policy makers to help consumers make informed choices about what they are eating.
The researchers highlight previous studies which produced conflicting results on whether calorie labelling alone was effective at helping people choose healthier foods and so they wanted to test the theory that adding physical activity information might be more effective.
What did the research involve?
The researchers recruited 802 US adults through the University of North Carolina weekly newsletter for employees.
Survey participants were randomly assigned to one of four menus:
- a menu with no nutritional information (used as the main comparison in the statistical analysis)
- a menu with calorie information
- a menu with calorie information and minutes to walk to burn those calories
- a menu with calorie information and miles to walk to burn those calories
An example label for a regular burger containing 250 calories indicated it would take 78 minutes to walk off the calories or the equivalent of walking 2.6miles.
Using a web-based survey, all participants were asked to ‘imagine you are at a fast food restaurant (like McDonalds, Burger King or Wendy’s) and are getting ready to order a meal for yourself. Please select what you would order from the menu below based on the information provided. The menu included sandwiches, sides, salads, salad dressing, drinks and desserts. Please select all items that you would order”. The sample menu was a composite of the online menus of common US fast food restaurants without any item pictures.
The researchers then compared the number of calories ordered across the three groups to see if different menu labelling had influenced food choices.
The remainder of the survey collected basic demographic information such as age, gender, race, occupation, current smoking, and education to ensure randomised groups were balanced. In addition, the survey collected variables that could explain variations in the calorie content of meals ordered among participants randomised to the same type of menu, including but not limited to: calorie literacy, body mass index (BMI) and exercise frequency.
The statistical analysis was appropriate.
What were the basic results?
The characteristics of the 802 randomised participants were well balanced between the four groups. Most participants were female (88%), had attended higher education (96%), were 40 years old or more (62%) and identified as white (71%). Most of the respondents were currently trying to lose weight (64%) and were trying to limit their calorie intake (65%).
There was a statistically significant difference in the average (mean) number of calories ordered based on the different menu types. The average number of calories ordered from each menu was as follows:
- 1,020 from the menu with no nutritional information
- 927 from the menu with only calorie information
- 916 from the menu with both calorie information and minutes to walk to burn those calories
- 826 from the menu with calorie information and the number of miles to walk to burn those calories
Hence, the menu with calorie information and number of miles walked seemed most effective at influencing the selection of lower calorie meals.
At the end of the survey, participants were asked to indicate which type of food labelling they would prefer to see on a menu. The largest proportion (45%) said they preferred the menu with calories and minutes to walk to burn those calories, 37% preferred the menu with calories and miles to walk to burn those calories, 13% reported the menu with calorie information only and 5% reported the menu with no nutritional information. Merging the groups showed that the majority (82%) preferred labels showing physical activity (time or distance) over menus with calorie information only or no nutritional information at all.
Interestingly, in other results they found only 31% of the sample answered all three questions testing their numeracy correctly, and only 8% of the sample answered all three calorie literacy questions correctly.
This suggests numerical calorie information may not be understood by the majority of women in the sample – arguably surprising considering 96% attended at least some college/university education.
How did the researchers interpret the results?
The researchers concluded that “comparisons between menu types suggest the miles to walk label may be the most effective in inﬂuencing the selection of lower calorie meals” and that “our results suggest people may be more responsive to physical activity information in the form of miles walked rather than minutes walked”.
They also raised the important point that, “whether these labels are effective in real-life scenarios remains to be tested”.
This study of 802, mainly middle–aged, US females indicated that labelling fast food menus with the calories and the distance it would take to work off the calories was more effective at influencing the selection of lower calorie meals than displaying calorie information only, or calorie information plus the amount of walking time it would take to burn it off.
Those using a menu containing no nutritional information chose around 1,020 calories on average compared to just 826 calories from the menu with calorie information and the number of miles to walk to burn those calories.
This was a difference of 194 calories or approximately 10% of a woman’s total recommended calories per day of 2,000 calories.
While this is not a massive amount (194 calories is just over the amount found in a standard bag of crisps), it could soon add up over the space of a month or a year.
The main strengths of the study include its relatively large sample size (n=802) and the randomisation of its participants to the four groups. This resulted in an even balance of characteristics across the four groups, providing a good starting point for the experiment.
However, the study does have limitations to consider that may influence the interpretation of the findings.
How representative was the sample?
The study sample represented a group of middle-aged women, most of whom were trying to lose weight and restrict their calorie intake. Their behavioural response to food labelling may be different from other groups such as men or those who are overweight but not actively trying to lose weight.
Similarly, numeracy levels in the sample were very low (only 8% answered three questions on numeracy correctly). The researchers also added “many Americans may have difficulty in interpreting percentages and proportions”. Hence, we should consider how closely this low numeracy group match the general population of the UK, because differences in numeracy levels may influence people’s response to calorie-only food labelling.
None the less, these results are likely to be of interest to public health professionals and the numerous middle aged women watching their waistlines this Christmas period.
Participants in this study were those that voluntarily responded to an employee newsletter highlighting the study. This introduces an unavoidable selection bias.
People motivated enough to respond to a survey dealing with the subject of calories and food labelling (which the researchers estimated was approximately 6% of the total newsletter readership) may respond differently to food labelling than those that didn’t respond. For instance, the group that didn’t take part may be less motivated to change their diet or weight, which may make them less responsive to labelling aimed at reducing calorie intake.
Another important limitation of the study is that it used a relatively hypothetical scenario of ordering fast food online. While this is possible for some takeaway services, this does not serve as a substitute for the more common real-world experience of ordering an actual meal in a fast food restaurant. The real-life scenario may also involve ordering with friends, which could add a social dimension not explored in the present study. Further studies will need to be conducted in real-world settings to see if similar results are obtained.
This intriguing study highlights the potentially large influence that food labelling can have on food choice. The most widely used food labelling system is the traffic light system, where colours are used to indicate levels of potentially unhealthy ingredients, such as fats, sugar and salt.
Possibly adding a real-world equivalent to the current labels (such as the walking distance needed to burn off the calories) would help people better understand the amount of the calories they are about to consume.
The next step would be to test whether these preliminary results are replicated in a more real-life scenario and in more diverse groups of people. Future studies could also benefit from looking at how far participants actually walk day to day and whether the labelling influenced physical activity patterns in any way.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.